Trafficlights

from gpiozero import LED
from time import sleep

#setup
#turn all leds off
red_led = LED(2)
ylw_led = LED(3)
grn_led = LED(4)

red_led.off()
ylw_led.off()
grn_led.off()

for i in range(0,6):
    #stop - wait
    red_led.on()
    sleep(3)

    #get ready
    ylw_led.on()
    sleep(1)

    #go
    red_led.off()
    ylw_led.off()
    grn_led.on()
    sleep(3)

    #prepare to stop
    grn_led.off()
    ylw_led.on()
    sleep(1)
    ylw_led.off()